RsJX“地图"运算符在Angular 6中不起作用 [英] RsJX 'Map' operator is not working in Angular 6

问题描述

我正在尝试使用RxJS中的map运算符，但会引发错误提示

I'm trying to use map operator from RxJS but it throws an error saying

可观察"类型不存在属性地图".

Property 'map' does not exist on type 'Observable'.

这是代码

    import { Injectable } from "@angular/core";
    import { Http } from "@angular/http";
    import "rxjs/add/operator/map";
    @Injectable()

    export class DataService {
     constructor(public http: Http) {}

     getData() {
       return this.http
        .get("https://jsonplaceholder.typicode.com/users")
        .map(res => res.json());
      }
    }

推荐答案

首先，Http的版本高于 Angular 4 .取而代之的是，您需要将HttpClient与"@angular/common/http"中的HttpClientModule一起使用.使用HttpClient您将获得 JSON 解析结果，因此您无需再花费res.json().

For first Http is deprecated in higher versions than Angular 4. Instead of it you need to use HttpClient with HttpClientModule from "@angular/common/http". And using HttpClient you will get the JSON parsed result, so you don't need res.json() longer.

在 RxJS 的新版本中，第二个map正在使用另一种方式.现在可以通过管道传输了，您需要将其与pipe结合使用.

For second map in new verions of RxJS is being used another way. It is now pipeable, you need to use it combined with pipe.

import { Injectable } from "@angular/core";
import { HttpClient} from "@angular/common/http";

@Injectable()    
export class DataService {
  constructor(public httpClient: HttpClient) {}

  getData() {
    return this.httpClient
               .get("https://jsonplaceholder.typicode.com/users")
  }
}

使用map运算符

import { map } from 'rxjs/operators';

...

someFunction() {
   this.httpClient.get("https://jsonplaceholder.typicode.com/users")
                  .pipe(map(res) => something with res);
}

...

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